[CVE-2026-89527][LOW] svcrdma: Use svc_xprt_put to free listener on create failure

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-89527
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: svcrdma: Use svc_xprt_put to free listener on create failure
Commit: ac1dd6002f758ab7dd3e737757e5a1bb1c0b38d6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ac1dd6002f758ab7dd3e737757e5a1bb1c0b38d6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89527
Analysis date: Sat, 12 Sep 2026 02:47:15 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-89527 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89527

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-89527	LOW	https://www.kernelcve.org/list/?q=CVE-2026-89527 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;*CWE-401;CWE-404;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'svc_rdma_create() used direct kfree() on the listener create failure path after svc_xprt_init() had already acquired a tracked network namespace reference. This bypassed the normal svc_xprt_free() cleanup path and could leak references when RDMA listener creation fails, potentially preventing network namespace cleanup or causing resource exhaustion after repeated failures. For the CVSS the PR:H because reliable triggering normally requires administrative control of SUNRPC/NFS RDMA listener creation on the victim. The issue is not directly network reachable and is triggered through local service configuration rather than incoming RPC traffic. Impact is denial of service through resource leakage or cleanup hang, with no supported memory corruption primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	YES	REMOTE INIT SIMPLEFIX ERRORPATH NETWORK  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Applied conservative floor/cap: raw score clamped from -1 to 0 because ActionableScore is non-negative.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Concrete persistent kernel resource/reference leak. `svc_xprt_init()` already acquired a tracked network namespace reference, and direct `kfree(cma_xprt)` bypassed `svc_xprt_free()`, which normally releases it.

Negative signals:

* -2 Host-admin-equivalent triggering requirement. Creating or reconfiguring an NFS/SUNRPC RDMA listener is a privileged service-management operation on the host.

Paranoid-only signals:

* +1 Potential accumulated cleanup/resource impact. Repeated listener creation failures could accumulate leaked references and delay or prevent network namespace cleanup, but this remains a resource-leak scenario rather than memory corruption.

Important non-awarded signals:

* Real UAF not awarded. The old vulnerable path is a missing destructor/put path, not a stale post-free use.
* Concrete repeated release/refcount not awarded. The module reference balancing in the patch prevents a double module put that would otherwise be introduced by switching to `svc_xprt_put()`. It is not evidence that the pre-patch vulnerable code performed a concrete second put on the same dangling object.
* Strong DoS not awarded. No immediate kernel crash, panic, or host-wide failure is established.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality and integrity impact not awarded.
* Remote reachability not established. This is service configuration / listener creation failure handling, not incoming RPC packet processing.
* ImportantCandidate not set because the established primitive is a privileged local resource/reference leak without unresolved memory-corruption leverage.

Repeated-release/refcount checklist:

* First release can end lifetime: not established for the vulnerable old path.
* Exact same reference survives to a second lifetime mutation: not established.
* Second operation is a real lifetime/refcount mutation in the vulnerable old path: no.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no.

3. Reachability analysis

The trigger is the failure path of `svc_rdma_create()` when `svc_rdma_create_listen_id()` fails during RDMA listener creation. This is reached through local host service configuration or transport creation for SUNRPC/NFS RDMA, not by ordinary inbound network traffic.

The complete trigger normally requires host administrative control over NFS/SUNRPC RDMA service setup. The supplied evidence does not show an ordinary unprivileged local path, a namespace-created capability path, or a delegated non-host-admin path that can complete the listener creation sequence. The presence of a network namespace reference does not make the complete trigger namespace-scoped.

Prior host setup exists in the practical sense that the RDMA transport/service must be configured and the listener creation path must be exercised. RDMA hardware or RDMA stack availability may be relevant operationally, but no separate rare-hardware penalty is needed because the host-admin privilege requirement already dominates the practical risk. No race is involved.

4. Primitive and severity interpretation

The exact primitive is a missing normal cleanup path causing a leaked network namespace reference. Direct `kfree()` bypasses the transport destructor path, so nested resources held by `svc_xprt` are not released.

This is not active structured UAF, not fixed stale storage UAF, and not a concrete repeated release/refcount UAF. The object is freed incorrectly from a resource ownership perspective, but no stale dereference, second lifetime mutation, controlled reclaim, callback use, or attacker-controlled post-free operation is established.

PrimitiveClass is `NONE` because the established issue is a privileged local resource/reference leak, not memory corruption, authorization bypass, ownership/COW violation, or security-boundary primitive. The demonstrated consequence is resource leakage and possible cleanup/resource DoS after repeated failures. The speculative consequence is broader resource pressure, but no Important-grade exploitation path is supported.

ImportantCandidate is `NO` because there is no meaningful unresolved corruption or boundary-bypass leverage. AutoDowngradeAllowed is `YES` because the issue is suitable for ordinary deferred handling if the affected configuration is present and no stronger downstream evidence exists.

Likely operational severity is Low-like / ordinary Moderate.

5. One-sentence report phrase

A privileged local failure path in `svc_rdma_create()` used direct `kfree()` instead of the normal `svc_xprt_put()` cleanup path, leaking a network namespace reference and potentially causing resource cleanup issues after repeated RDMA listener creation failures.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch establishes a privileged local resource/reference leak only, with no UAF, repeated lifetime mutation, memory corruption, authorization bypass, remote trigger, or plausible privilege-escalation primitive.

7. Call-site confidence

Call-site confidence: high

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: svcrdma: Use svc_xprt_put to free listener on create failure
Commit: ac1dd6002f758ab7dd3e737757e5a1bb1c0b38d6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ac1dd6002f758ab7dd3e737757e5a1bb1c0b38d6

Commit description:

svc_rdma_create() calls kfree(cma_xprt) when
svc_rdma_create_listen_id() fails. svc_xprt_init() has already
acquired a net namespace reference via get_net_track(); kfree
bypasses svc_xprt_free() which releases it.

Replace the kfree() with svc_xprt_put() so the kref_init birth
reference drops to zero and svc_xprt_free() dispatches
svc_rdma_free() to clean up properly. sc_cm_id is still NULL
at that point; the preceding patch added the necessary NULL
guard in svc_rdma_free().

svc_xprt_free() also drops the module reference via
module_put(), but the caller _svc_xprt_create() does the same
on xpo_create failure, double-putting the single
try_module_get() it acquired. Take a compensating
__module_get() before the svc_xprt_put() to keep the count
balanced, matching the convention in svc_rdma_accept()'s error
path.

Fixes: 4fb8518 ("sunrpc: Tag svc_xprt with net")
Cc: stable@vger.kernel.org
Acked-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260527-rdma-follow-on-v1-3-1b09bd87b6cd@oracle.com
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/sunrpc/xprtrdma/svc_rdma_transport.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ac1dd6002f758ab7dd3e737757e5a1bb1c0b38d6

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-89527 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89527

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: unknown
  Paranoid ActionableScore: 0

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).